Programming Bioelectronic Bacteria as Real-Time and Multiplexed Sensors & Actuators

Challenged by a changing climate, dwindling natural resources, and a growing global population, we need renewable advanced materials that meld the sustainability of biology materials with the functionality of conventional materials. To help address this need, my research group engineers microorganisms as bioelectronic sensors and actuators by re-programming naturally-occurring pathways from microbes that transfer electrons to and from materials in their environment.<br/><br/>In my talk, I will first report how we have created bioelectronic sensors that convey multiple channels of information. Existing bioelectronic sensors can sense a variety of hazards to human and environmental health, however, these sensors transmit information through only a single electrochemical channel. This severely limits the amount of sensing information that can be transmitted. To increase this information content, we developed a multichannel bioelectronic sensor in which different chemicals modulate distinct extracellular electron transfer pathways in <i>Escherichia coli</i>. To create an <i>E. coli</i> strain with two reporting channels, we introduced a riboflavin synthesis pathway from <i>Bacillus subtilis</i> alongside the metal reducing (Mtr) pathway from <i>Shewanella</i> <i>oneidensis</i>. We can distinguish whether one or both pathways are active in this strain using amperometric measurements at distinct redox potentials. To demonstrate multi-channel bioelectronic sensing, we regulated the Mtr and riboflavin pathways using arsenic and cadmium responsive promoters. With this strain, we used a series of amperometric measurements at distinct redox potentials to distinguish the presence of the different heavy metals <i>in situ</i>. These accomplishments provide a new platform for multichannel bioelectronic sensors that simultaneously detect and report multiple toxins.<br/><br/>Next, I will describe how we have utilized the probiotic bacteria <i>Lactiplantibacillus plantarum</i> to sense and actuate via electronic signals. <i>L. plantarum</i> is known to utilize exogenous small molecule quinone mediators to perform extracellular electron transfer, which allows it to produce a detectable current. Different 1,4-naphthoquinone mediators yield significantly different current outputs. Using a library of 30 mediators, we probed the important physicochemical properties and biochemical interactions of quinones that are responsible for extracellular electron transfer in <i>L.</i> <i>plantarum</i>. We find that extracellular electron transfer is correlated most strongly to the mediator's polarity and binding affinity. Furthermore, we identify that amine containing mediators yielded incredibly stable current output over 5 days. These findings increase our understanding of structure-activity relationships for quinone-mediated EET and provide mediators for bioelectronic sensing.